Authorities say the deadliest attack happened in the north Baghdad neighborhood of Shaab, killing five people and wounding 15.

There was no immediate claim of responsibility, but Shi'ites and Sunni Islamists have a history of sectarian strife resulting in violence.

U.N. data show more than 5,000 people have been killed in militant attacks in Iraq since April when Shi'ite-dominated security forces attacked a Sunni protest encampment north of Baghdad.

Analysts have warned that the surge in violence -- the worst since 2008 -- threatens the return of widespread sectarian killing that pushed the country to the brink of civil war in the years after the 2003 U.S.-led invasion.